The hreflang x-default attribute value is used in international SEO to designate the fallback page that Google should show to users whose language or region does not match any of the specific locale variants declared in a site’s hreflang annotations. It is implemented as a standard hreflang link element with the value “x-default” in place of a language-region code, for example hreflang=“x-default”. Common use cases include a language-selection landing page, a generic English page intended for any English-speaking market not covered by a dedicated country URL, or a homepage that serves as a universal entry point. Without an x-default tag, users in uncovered locales may be served an arbitrary locale variant. Google recommends including x-default in any hreflang implementation that does not comprehensively cover every possible user locale.